1. Field of the Invention(s)
The invention(s) relates to surface modification of inorganic particles, and in particular to surface modified inorganic particles suitable for use as a flame retardant.
2. Description of the Related Art
Plastic and its composites are widely used in various fields such as sports equipment, indoor decoration materials, building materials, industrial and civil engineering, electronic products, automobile, and so on. However, because plastics are flammable materials, fires caused by plastic materials result in enormous personnel casualty and financial losses every year. It is therefore an important research topic to develop an environmentally-friendly fire resistant polymer material or composite that effectively reduces personnel casualty and financial losses due to plastic material fires, while also not causing pollution to the ecology.
Due to growing environmental concerns, there is a clear trend and need to develop halogen-free flame retardant systems. Examples of halogen-free flame retardants include magnesium hydroxide, and aluminum hydroxide. The flame retardant effects of aluminum hydroxide and magnesium hydroxide are based on endothermic decomposition into metal oxide and water, respectively. The plastic is protected from rapid thermal decomposition and the formation of flammable and combustible breakdown products are inhibited. The water vapor that is formed displaces the oxygen and functions as protective gas. A heat resistant covering layer including carbonized products and metal oxide is formed on the surface of the plastic inhibiting further combustion, which also reduces the smoke density by absorbing the combustion products. As the most popular halogen-free flame retardant, metal hydroxide can be used independently or in combination with other flame retardants to provide fire resistant thermosetting or thermoplastic composites.
Metal hydroxide, for example, aluminum trihydroxide (ATH), includes many —OH groups and usually has moisture adhered to its surface, and therefore has a very high polarity. Therefore, when metal hydroxide is blended with polymer resin, which generally has a low polarity, agglomeration occurs due to poor interfacial compatibility. In addition, because the polymer does not react with metal hydroxide to form a well-structured composite by the formation of chemical bonds, the resulting product easily melts, ignites, or produces flame drippings under exposure to flames. Moreover, the incorporation of metal hydroxide greatly increases the brittleness of the material, thus limiting application fields.
Accordingly, there exists a need for an inorganic particle having improved polymer compatibility to provide better flame retardancy and reduced brittleness.